Whatever you're doing in Australia, you're going to need a visa. There are a few different types of visas, but you're probably interested in one of these three:
Up to three months - If you’re visiting purely as a tourist for three months or less, an Electronic Travel Authority or ETA is the easy alternative to a visa. It doesn’t cost much, only a AU$20 administration fee - your travel agent or airline can sort one out for you.
If you decide once you're there that you want to stay a bit longer, you should be able to extend your ETA to last you an extra three months. To do this, go to an immigration office in Australia.
Three to six months - If you want to go for three to six months, you'll need to apply for a long-term tourist visa. To do this, you'll have to download and fill in a form, and send it to your nearest Australian High Commission. You'll also need to pay AU$50, and send various documents, including proof that you can support yourself in Oz (for example, a bank statement, letters from a bank concerning your financial position, air tickets that have been purchased).
The UK and many other countries have reciprocal agreements with Australia so any citizen aged 18 to 30 can get a working holiday visa. They cost AU$270 and allow you to work for 12 months from the date you arrive in Australia. You can extend that and obtain a second-year working holiday visa if you can provide evidence that you undertook 88 days of agricultural work (for example, fruit picking) in Australia during your first year. However, you can’t work for the same employer for more than six months. Australian authorities check every one in four visa applications, so don’t run the risk of applying in the hope of being overlooked.
To be issued a working holiday visa you need proof that you can support yourself - AU$5,000 is advised by the Australian Government. You can apply online for a working holiday visa and it only takes a couple of hours to complete.
You can leave and re-enter Australia using this visa as many times as you like during your year. However, if you permanently leave Australia without staying for the full 12 months you cannot go back, say, a year later and use the remaining months of your visa.
Once your visa has been approved you will be told what you need to do. Basically, your passport will be stamped when you arrive and you'll have a year before you have to leave. Simple really. Everything is tagged electronically so there's no paper-work to worry about.
If you want to study (where better to do marine biology than on the Great Barrier Reef?), the Australian government operates an overseas student programme (OSP) that allows people who are not Australian citizens or permanent residents to study in Australia.
Anyone who is not an Australian resident may apply to study in Australia under the OSP. If you want to study under this programme, you’ll first need a student visa. You can only get one of these if you wish to undertake a registered course or part of a registered course on a full-time basis.
You can’t go out to Oz and then look around for courses. Before you apply for an Australian student visa, you’ll need a letter of acceptance or electronic confirmation of enrolment from your education provider. Types and prices of student visas vary, and there are various requirements you’ll need to fill (including being of 'good character’).
The visa is easy to apply for and can be done online. Student visas last for two to four years and cost AU$535. You can work on a student visa too, but you need to be in education for at least four months of the year. Also, many UK universities offer placement years in Australia.